This invention relates generally to the field of solderable electrical connectors, and more specifically to a component and method used for making electrical connections to a printed circuit (PC) board or the like.
Various devices are available in the prior art to establish a mechanical and electrical connection between two current-carrying elements. The majority of these connectors involve the mating of male and female component members. In one category of such connectors a spring-loaded or resilient surface on one of the members is placed into contact with a cooperatively shaped surface on the other member. The resiliency then holds the two members together in electrical contact until a separating force is applied to the connector which is sufficient to overcome the retaining tension.
While these resiliently mating connectors provide a convenient device for rapidly making or interrupting electrical connection between two current-carrying members, the resulting connection may not be reliable enough for permanent use in some instances. It is therefore frequently desirable to solder the connection to prevent mechanical separation of the connecting members and to improve the conductivity of the electrical junction. This is especially true in the case of PC board connections, in which the electrical and mechanical quality of the connections must be assured for reliable operation.
Techniques for providing such soldered connections are known in the art, by which a quantity of solder is melted adjacent the junction of two members so that the solder flows, by gravity or capillary action, over the adjacent or abutting surfaces of the members to be soldered. However, when the members to be soldered are closely mating elements, a problem is frequently encountered because of the difficulty of assuring solder flow into the region where the mating members meet.
An example of this occurs in the so-called "Tri-socket" connector for making connection to a throughplated hole on a PC board. This connector, for example, may have a socket at one end for establishing an electrical connection with a pin of a dual in-line (DIP) package when inserted into the socket end of the connector, and a wire wrap post at the other end of the connector around which may be wrapped a wire from an external circuit. This connector also has a resilient tricornered fin arrangement in the middle of the connector, which upon insertion into a plated hole of a PC board is compressed resiliently against the wall of the hole. A rivet of solder is carried by the connector above the resilient arrangement, the rivet resting above the PC board when the resilient arrangement is within the PC board hole. The connector is then soldered in place by heating, as in a heating chamber, which allows the solder rivet to melt and flow into the hole to bond the fin arrangement to the plated hole.
Soldered connections formed with contact elements such as this Tri-socket connector may have mechanical or electrical flaws if the soldering process is not carefully monitored. Since the solder is initially located outside the hole in the PC board before being heated, the soldering process must be planned so that melting solder will flow properly into the hole and then adhere well to both the plating surrounding the hole and the prongs of the contact element. However the flow pattern of the melting solder may be affected by a number of variables, such as the temperature of the solder and the mating members, the angle at which the members are soldered, the shapes of the mating members, and the shape of the path over which the melted solder will run. The resulting unpredictability of this flow pattern may produce mechanical and electrical inconsistencies in the soldered connections which are not apparent from visual inspection. Thus, if the board and connector are not accurately aligned during heating to allow the solder to flow properly into the hole, the resulting connection may be mechanically weak because insufficient solder may reach the connecting region. If solder flows before the mating elements have been heated to the proper temperature, the resulting junction may be electrically poor due to the formation of a "cold joint". Even if the solder flows properly into the hole and adheres well to both connecting members, it may not get close to the region where the surfaces of the mating members are in contact. If the solder could be reliably introduced to this region the electrical junction would be improved and the resulting bond would be considerably strengthened, as it would provide a very thin layer of solder between two substantially conforming surfaces.